A hydraulic piston machine has cylinder-piston units each with a piston or working piston displaceable axially in a cylinder. The piston is held with a piston head in a concave recess of a sliding block which is preferably made of nonferrous metal or steel. Via the sliding block the piston can be supported on a sliding surface or a swash plate of the piston machine. During operation of the piston machine, the sliding block must tolerate piston support forces which are substantial depending on the working pressure of the piston machine or the viscosity of the hydraulic fluid. Under this mechanical load, firstly wear can occur because of the sliding friction and secondly breakage of the sliding block.
To reduce this risk, the sliding surface of the sliding block is lubricated. This is achieved by means of a lubricant channel which passes through the sliding block from its concave recess to its sliding surface and via which lubricant or hydraulic fluid is delivered to the sliding surface. It is also known that the lubricant channel opens into a relief recess of the sliding surface of the sliding block, improving lubrication and relieving the load on the sliding block.
For this, U.S. Pat. No. 6,555,777 B1 discloses two embodiment examples of a sliding block with a lubricant channel arranged centrally. The lubricant channel of the first embodiment example opens via a small concave spherical cap with a sharp edge into the concave recess and with a long thin bore into a relief recess of the sliding surface. The lubricant channel of the second embodiment example opens via a broad cylindrical bore also with a sharp edge into the concave recess and with a frustoconical expansion into the sliding surface.
A sliding block shown in DE 3210146 A1 has a central lubricant channel which transforms via a broad cylindrical bore with a sharp edge into the concave recess. Adjacent to the cylindrical bore in the direction of the sliding surface is a frustoconical expansion which transforms into a narrow cylindrical bore which in turn opens into a relief recess of the sliding block. The transitions between the cylindrical bores and the frustoconical expansion are in this case sharp-edged.
The disadvantage of the solutions of both publications is that at the sharp-edged transitions of the lubricant channel, the sliding block is exposed to a high stress concentration which reduces the strength.
Publication EP 0763657 A1 shows a sliding block with reduced stress concentration at the lubricant channel. This has no sharp edges at the transition into the concave recess or into the relief recess. The concave recess transforms with a constant tangent, i.e. without kinking, into a frustoconically narrowing segment of the lubricant channel, which in turn transforms via a rounding into a cylindrical segment of the lubricant channel, which finally opens into the relief recess.
The disadvantage of this sliding block is that the large frustoconical segment can no longer serve as a support surface for the piston head, so that a substantial proportion of the support force to be absorbed by the sliding block is unfavorably transferred radially into the sliding block, which can lead to a fission of the sliding block.
In view of this, the object of the disclosure is to create a sliding block with increased strength.